In the field of automated assembly it is common to use linear actuator systems with either a servo-controlled motor for positioning or a pneumatic pressure device for positioning. Servo-controlled systems can become very costly and large in meeting demands for moving large loads at quick velocities, the latter being critical in minimizing cycle time. Pneumatic systems offer the ability accelerate and move large loads quickly, but at the cost of being able to programmably control positioning, velocity and acceleration.
Some solutions have been attempted at combining the benefits of both types of positioning control. In one solution a pneumatic cylinder overrides the servo-controlled motor to provide coarse positioning. Once the coarse position is reached, the servo-controlled motor moves the load to the desired final position.
It has been determined that an optimal solution can be achieved by leaving a servo controlled device engaged for position, acceleration and velocity control across the full range of movement of the load. A fluid-power boost is provided concurrently with the servo-positioning scheme to assist in the rapid coarse movement. The fluid boost provides a first pressure boost in one direction of movement and a second pressure boost in the opposite second direction of movement, wherein the first and second pressures are different. This has proven especially beneficial in the moving of loads against and with the gravitational force associated with moving vertically.
While various approaches have been proposed in the art to address maximizing both speed and control in linear actuator systems, there nevertheless remains a continued need for improvements in the art, and it is to such improvements that the present invention is directed.